A team of volcanologists led by Kate Saunders of the University of Bristol in England said they've linked earthquake swarms at Mount St. Helens in Washington with fresh magma pulses by studying rock crystals formed during the 1980-86 eruptions, ScienceNews.org reported.
These crystals of a mineral called orthopyroxene grow in zoned "rims," the researchers said, each one formed as fresh magma arrives from below the volcano and cools.
The calculated when the crystals grew and compared that with the timing of small earthquakes shaking the mountain, finding in many cases a link between the crystal rim growth and swarms of seismic activity.
Studying crystals ejected from other volcanoes could help scientists better understand how often new magma arrives, the researchers wrote in the journal Science.
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